mysql: fix compilation on bison 3.x

- From now on it's possible to use Debian 9.1.0 with latest bison from repo

release/src-rt-6.x.4708/router/Makefile

@@ -2143,6 +2143,9 @@ libncurses-install:
 
 mysql/stamp-h1: openssl zlib libncurses
 	@$(SEP)
+	( if ! patch -R -f -d mysql/sql --dry-run --silent < patches/mysql/101-bison-compat.patch; then \
+		patch -b -d mysql/sql < patches/mysql/101-bison-compat.patch; \
+	fi ) && \
 	cd mysql && cp -f configure.arm configure && \
 	CFLAGS="-O2 -Wall -fno-delete-null-pointer-checks -funit-at-a-time --param large-function-growth=800 \
 		--param max-inline-insns-single=3000 -ffunction-sections -fdata-sections -I$(TOP)/zlib \